Internal-combustion engine



Oct. 26, 1954 BARBER 2,692,587

INTERNAL-COMBUSTION ENGINE Filed June 25, 1952 2 Sheets-Sheet 2 INVENTOR. EVERETT M. BARBER gwm ATTORNEY Patented Oct. 26, 1954 INTERNAL-COMBUSTION ENGINE Everett M. Barber, Wappingers Falls, N. 31., as-

signor to The Texas Company, New York, N. Y., a corporation of Delaware Application June 23, 1952, Serial No. 295,023

15 Claims. 1

This invention is concerned with internal combustion engines and their operation and provides methods and apparatus for igniting the charge in a particular type of internal combustion engine, of which one example is described and claimed by E. M. Barber in U. S. Patent No. 2,484,009.

The internal combustion engines here considered are of the reciprocating type. Fluid fuel to be burned in the engine is injected each cycle and is formed into a patch of combustible mixture which is confined in one direction by a stream of oxidizing gas traveling toward the patch and containing little or no vaporized fuel, so that it is incombustible. The patch is confined on the other side by gaseous products of combustion traveling away from a flame front on the patch, where the mixture is burned substantially as fast as it is formed. As a result, little or no end gases are permitted to exist, and even when existent are not exposed to the pressure and temperature and for the time required to bring about spontaneous ignition.

In the preferred form of engine operations to which the instant invention applies, the oxidizing gas for the combustion is caused to form a compressed rapidly swirling mass in the engine cylinder. The fluid fuel, which may be either gaseous or liquid, is injected into the compressed swirling mass of oxidizing gas so as to impregnate a localized segment of the swirling mass and form the combustible patch. The first increment of the patch is ignited substantially as soon as it is formed, the ignition taking place near the locus of fuel injection. Thus a flame is formed at the front of the patch. This flame front tends to travel in a direction counter to the swirl toward the locus of fuel injection. The combustion products formed in the burning patch travel in the direction of swirl away from the flame front, and the flame front is fed by successive increments of combustible mixture swirling toward it and formed of fuel injected into the swirling oxidizing gas. The successive increments of combustible mixture are burned in the patch at or near the flame front substantially as fast as they are formed during each combustion period of the engine, the injection of fuel ceasing as soon as suflicient fuel for each power stroke has been injected. The combustible patch of mixture is thus confined on one side by an incombustible layer of the combustion products swirling away from the patch and on the opposite side by an incombustible layer of oxidizing gas into which no fuel has yet been injected or which does not yet contain enough vaporized fuel to form a combustible mixture. Combustion is thus confined to and completed in the patch. Under these conditions substantially no end gases are formed, and even if formed, do not attain the 2 temperature, pressure and density at which spontaneous ignition tends to occur. Consequently ping or knock is inhibited even with fuels of low anti-knock value at high compression ratios.

The combustible mixture which constitutes the patch to be burned may be ignited by conventional means such as a spark or glow plug disposed in the cylinder in the locus of the patch. However, I have discovered that it is also possible to ignite this main patch of combustible mixture by forming a pilot patch of combustible mixture separate from and before the main patch. This pilot patch is permitted to swirl toward the locus of fuel injection while it is being compressed, the degree of compression and the time for compression of the pilot patch being such that the pilot patch ignites just about the time that it is carried past the locus of injection of the fuel which forms the main patch. The flaming pilot patch ignites the first increment of combustible mixture in the main patch and thus produces the required flame front. Thereafter the process proceeds as described previously.

Preferably, the pilot patch is formed by injecting fuel into the cylinder in a short burst substantially in advance of the beginning of fuel injection for the main patch, the particular instant for injection of the fuel for the pilot patch being governed by the swirl rate of the oxidizing gas in the cylinder. If desired, the fuel for the pilot patch may be different from that employed as the principal fuel in the engine, 1. e. that employed to form the main patch. In such case an additional injection system is employed, Or the fuel for both main and pilot patches may be the same, in which case a single injection system, timed to deliver the separate jets or sprays, is preferred.

The use of a pilot patch for ignition purposes in accordance with the invention may be employed in both two cycle and four cycle engines of the type here considered. The formation of the pilot patch should be coordinated with the swirl rate so that it is carried past the locus at which the main patch is formed at the proper instant, i. e. while it is flamingthis being the same time that the first increment of combustible mixture for the main patch is formed.

The fuel for the pilot patch may be injected at the same point that the fuel for the main patch is injected, in which case the pilot patch can make one or more complete swirls in the engine before igniting. However, it is also feasible to inject the fuel for the pilot patch at a different point on the circumference of the cylinder, providing that cetane rating, swirl rate, time for compression, and degree of compression are so related that the pilot patch flames at the location and time required to ignite the first increment of the main patch.

The duration of fuel injection for the pilot patch should. be short compared to the duration of fuel injection for the main patch, to assure that the pilot patch is small and isolated. To keep the pilot patch in this condition and to prevent it from mixing too much with the surrounding swirling air or other gaseous oxidant with resultant excessive dilution, turbulence should be avoided and if possible the oxidant should swirl with constant angular velocity, as described and claimed in my co-pending application, Serial No. 284,075, filed April 24, 1952, having the same assignee as this application.

These and other aspects of the invention are explained in greater detail with reference to the accompanying drawings, in which:

Fig. 1 is a composite graph illustrating one scheme of timing injection of the fuel for form.- ing the pilot and main patches, and what happens in the engine with such timing;

Fig. 2 is a diagrammatic vertical section through an engine equipped to practice the in.- vention and employing a single fuel supply;

Fig. 3 is a diagram partly in vertical section of an engine equipped for the practice of the invention employing different fuel supplies for the pilot and main sprays; and

Fig. 4 is a partial plan section of the engine of Fig. 3 showing the location of a glow plug which may be employed for ignition purposes, instead of the pilot patch, once the glow plug has been sufficiently heated.

The engine illustrated in Fig. 1 is an Otto .or

four cycle engine of the type described in U. S. Patent No. 2,484,009, except that it is not pro vided with spark or glow plug for ignition. It comprises a cylinder l provided with a shroud-v ed poppet valve H on its air intake l2, the shroud being so placed that it causes the air to swirl rapidly around the axis of the cylinder as it is drawn in on the intake stroke. The swirl thus induced is geared to the engine crank shaft, i. e. the rate of swirl bears a substantially constant ratio to engine R. P. M. regardless of changes in engine speed. This ratio may be al tered by changing shroud and port design, but for four cycle engines of the type here considered, satisfactory operations are obtained when the swirl rate is about six times engine Speed in R. P. M. Fig. 1 has been drawn on the assumption that this swirl rate obtains, the direction of swirl being counterclockwise as viewed in the several plan diagrams across the top of the f gure.

The engine is provided with a conventional exhaust poppet valve l3 in its head I l, and with a single fuel injection nozzle l5 which projects through the wall of the cylinder and directs a spray of liquid fuel, say diesel oil, downstream but across the swirling air in the cylinder.

The air swirls counterclockwise, as viewed in the plan diagrams at the top of Fig. 1, the rate of swirl being six times the engine speed in R. P. M. The swirl of the air is induced as it is drawn in during the intake stroke (not shown in Fig. 1), but persists during the compression stroke, which begins when the piston ll starts to move up from bottom dead center (B. D. C.). When the piston has moved up 90 of crank angle, fuel is sprayed into the cylinder for a brief interval ("5 crank angle degrees) as indicated in column A of Fig. 1. This fuel is immediately entrained in the swirling air to form a small pilot patch l8 which continues to swirl around in the cylinder as the piston rises and compresses the air containing the moving pilot patch. Since the rate of swirl is six times the engine R. P. M., the pilot patch makes one complete swirl as the piston rises an additional 60 of crank angle and arrives at 30 below top dead center (T. D. C.) as indicated in column B of Fig. 1. The cetane number of the fuel composing the pilot patch is so chosen that the patch ignites by compression just as it completes its first swirl and returns past the injection nozzle. At that instant, the first increment of fuel for the main patch is injected, and as the first increment of the main patch is formed it is ignited by the pilot patch (column B). When the first increment of the main patch 20 is ignited, the flame front is established. This front tends to burn toward the injector, and consumes additional combustible mixture formed as the fuel injection for the main patch continues for a time interval that is slightly less than that required for one air swirl (say 50 of crank angle). The main patch, its flame front 2|, the gaseous combustion products 22 swirling counterclockwise away from the fiame front, and the incombustible air 23 swirling in the same direction toward the main patch are shown in column C of Fig. 1, which illustrates the condition in the engine just as the fuel injection for the main patch ceases and the piston has been lowered 2O crank angle degrees from its position at top dead center, i. c. after 50 crank angle degrees of fuel injection.

The power stroke continues as the gases continue to expand until the piston reaches bottom dead center again, when the exhaust valve opens and the exhaust stroke begins. The ex.- haust stroke continues for approximately 130 crank angle degrees, when the intake valve is opened and the exhaust valve closes, after which the intake or suction stroke of the engine proceeds in the Otto cycle while the infiowing air is caused to swirl. In this fashion, the engine passes through the complete Otto cycle of 720 crank angle degrees, and the operation begins again, as previously described, i. e. the piston rises degrees of crank angle from bottom dead center, the fuel for the pilot patch is injected for about 5 crank angle degrees, etc.

In the preferred form of the combustion process illustrated in Fig. l, the pilot patch is formed so that it makes approximately one complete swirl before igniting itself and in turn firing the first increment of the main patch. This timing arrangement subjects the pilot patch to compression for an interval of time which is sunficient to cause the patch to ignite, yet the interval of time is short enough to preclude appreciable diffusion of the patch which might impair its usefulness as a source of ignition.

It is not necessary for the practice of the invention that the pilot jet be introduced at the same point on the cylinder periphery as the main jet. For example, if the cetane number of the fuel is such that the pilot patch can be ignited during the time required for one and one-half swirls or 90 crank angle degrees the pilot injector may be located opposite the main injector 0n the cylinder wall at 24 (see column A). Then the pilot injection would begin 90 crank angle degrees ahead of the time when the main injection occurs, and the pilot patch should then swirl approximately one and a half times before igniting itself and firing the first increments of the main patch.

The particular crank angle degrees shown in Fig. 1 are for purposes of illustration only. The beginning of injection of fuel for the main patch may begin at either side of top dead center, de-

' pending upon engine load. The beginning of injection of fuel for the pilot patch may begin at almost any time during the compression stroke, provided that the fuel which forms this patch is such that it will be burning at the time and place required for igniting the main patch. Simi larly, the duration of injection of fuel for the pilot patch may be varied considerably, bearing in mind that this duration should be relatively short compared to the duration of injection of fuel for the main patch, so as to preserve the pilot patch as an entity, and leave in the cylinder a mass of swirling air which contains so little fuel that it will not ignite and will serve to blanket and confine one side of the main patch, as illustrated in column 0 of Fig. 1.

It should also be pointed out that the duration of injection of fuel for the main jet (50 crank angle de s n Fig. 1) is by way of illustration only, and that this duration may be varied considerably, depending upon the load placed on the engine. Generally speaking, it is desirable in an engine of the type described here to throttle the fuel for the main jet, rather than the air, in order to assure the isolation of the burning main patch at front and rear and thus preserve the conditions under which spontaneous ignition of any portion of the main fuel injection is inhibited.

Fig. 2 illustrates a four cycle engine of the type shown diagrammatically in Fig. 1, except that in the engine of Fig. 2, the direction of swirl is clockwise. It comprises a cylinder 36 provided with a cooling jacket 3| and a head 32 also provided with cooling channels 33. An air inlet port 3 2 in the head opens into the cylinder through a poppet valve 35 provided with a semi-circular shroud 35A on its rear side, as viewed in Fig. 2. An exhaust port 36 in the head opens from the cylinder through a conventional poppet exhaust valve 3?. A conventional piston 38 provided with rings 39 reciprocates in the cylinder. lhe piston is also provided with the conventional connecting rod and crank shaft (not shown). A fuel injector nozzle ll projects into the upper portion of the cylinder above the top dead center position of the piston and sprays fuel across the swirling air stream therein. The nozzle is connected by a pipe ll to a fuel valve 42 equipped with a pressure feed line 43 and a valve stem or plunger 44 that is moved by a cam 45. The cam is geared to the crank shaft by conventional means (not shown) and makes one complete revolution for each two revolutions of the crank shaft.

The cam 45 is journaled on a center pin 56 and is circular in cross section except for a small protuberance or pilot boss ll which brings about the injection of the pilot spray and a large or main boss 48 which brings about the injection of the main spray.

At the instant shown in Fig. 2, the intake stroke has begun and the piston is traveling downward at 30 crank angle degrees from top dead center. The intake valve is open and the air being sucked in is induced to swirl around the cylinder in a clockwise direction (see Fig. 4). The cam is being driven clockwise by the crank shaft and the small or pilot boss has about 120 cam degrees or 240 crank angle degrees to travel before it strikes the plunger to push it in and cause the pilot spray to enter the cylinder. Accordingly,

the pilot spray will begin 240 crank angle degrees from the instant shown in Fig. 2, or at the instant that the piston, having completed its intake stroke, has risen 90 crank angle degrees on the compression stroke. By that time, of course, the air intake valve will be closed. The pilot boss on the cam occupies, say 2 cam degrees, or 5 degrees of crank angle, so that the pilot spray will endure for about this interval.

Assuming that the configuration of air intake port and valve is such that the air makes 6 swirls for each engine revolution, as in the apparatus of Fig. 1, then the pilot patch formed in the cylinder as a result of the pilot injection will make one complete swirl while the piston is traveling upward 60 degrees of crank angle on its compression stroke toward top dead center. In this interval the cam will have traveled about 60 crank angle degrees or 30 cam angle degrees, and this will bring the second or main boss into contact with the valve plunger and hold it down for the width of the boss (say 25 cam degrees or 50 crank angle degrees). During the interval that the plunger is held down, fuel to form the main spray will be injected.

If the cetane number of the fuel is properly chosen the pilot patch introduced as a result of the action of the pilot boss will be burning as it swirls past the injection nozzle as the first increment of the combustible main patch is formed. Thus the main patch is ignited, and the process thereafter continues until the cycle is completed, as described in connection with Fig. 1, no more fuel being injected until after the balance of the power stroke, the complete exhaust and intake strokes, and the first 90 crank angle degrees of the compression stroke have been completed.

The engine illustrated in Figs. 3 and 4. is in general similar to the apparatus of Fig. 2, like parts being designated by like reference characters. It differs, however, in being provided with two separat fuel injection systems plus a glow plug adapted to ignite the main patch after the glow plug has become incandescent as a result of the 1 heat of combustion developed in the engine.

Thus in the apparatus of Figs. 3 and 4, the main injector nozzle iii is connected by its line M to the plunger operated valve 42. The plunger i l of this valve is controlled by a separate cam 50 which is journaled on a pin 5| and bears against the plunger. The valve 42 is supplied with fuel from a separate supply tank 52 which feeds a high pressure pump 53 through a pipe 54. The outlet of the pump is a pipe 55 which leads to an accumulator tank 56. This in turn is connected to the control valve through a check valve 57 and the valve inlet line 43.

The engine of Figs. 3 and 4 is provided with a second or pilot injector nozzle 58 which is connected to a control valve 59 through a pipe 50. This control valve has a plunger or stem 5| which is operated by a pilot cam 62 that is journaled on a pin 63 and bears against the end of the plunger. Liquid fuel of high cetane number is supplied to the control valve from a separate supply 64. This is connected by a pipe 65 to a high pressure pump 66, the outlet of which is connected to an accumulator tank El through a pipe 58, The outlet of the accumulator tank is connected by a pipe 69 to the control valve and contains a check valve '10.

Both fuel injector systems may be patterned after conventional diesel injection systems. Their respective cams are geared to the crank shaft of the engine by conventional means, not

shown, and so synchronized with the engine rotation that the pilot spray and the main spray are injected at the instants and for the durations previously described with reference to Fig. 2.

The pilot injector and the main injector are disposed parallel to each other, with the pilot injector nearer the piston. Both jets are sprayed fan-wise downstream across the swirling air in the cylinder.

In addition to the two injector systems, the apparatus of Figs. 3 and 4 is provided with a glow plug '72 screwed into the wall of the cylinder and provided with a member 13 of high specific heat. This member is heat-insulated from the rest of the plug and is placed at a location in the cylinder just ahead of the injectors, i. e. at a proper location to ignite the first increment of the main patch, once the glow plug has become hot enough.

In the operation of the engine of Figs. 3 and 4, it is started employing the two injection systems. Fuel of high cetane number is introduced as the pilot jet. The pilot patch formed from this fuel is compression-ignited at the proper instant to fire the first increment of the main patch, which then burns as previously described, the operation being repeated until the heat-holding member of the glow plug has become hot enough to ignite the main patch by itself. Thereafter the pilot injection system may be shut down, until starting again becomes necessary.

The invention makes possible the operation of an engine of the type described without employing a spark or other electrical ignition system. It is particularly useful in large stationary engine installations, but may be employed in a variety of installations and with a variety of fuels. It is only necessary that the fuel for the pilotpatch be capable of compression-ignition at the proper time. The fuel for the main patch may be almost any combustible fluid, such as natural gas, gasoline, kerosene, diesel fuel, or even heavier hydrocarbons, for neither octane rating nor cetane rating is critical insofar as the main patch is concerned.

To prevent the pilot patch from being sheared and diluted. the air swirl should approximate that of a solid body, i. e. the angular velocity of the swirling air should be substantially constant, irrespective of the radius at which it is measured. Suitable structures for achieving such solid body swirl especially in two cycle engines, are disclosed in my previously identified co-pending application.

The application of the invention to the operation of two cycle engines is the same as that for Otto cycle engines, bearing in mind that the pilot patch should be introduced into the engine on the compression stroke early enough in the cycle that it is burning as it swirls past the locus of fuel injection for the main patch and. not so early that it has spent itself by this time and so cannot ignite the main patch.

I claim:

1. In conducting a cycle of a reciprocating internal combustion engine wherein combustion of a main combustible mixture is localized in a patch in a cylinder into which fuel is injected substantially as fast as it is burned and which is confined in one direction by oxidizing gas traveling toward the patch and containing so little fuel that it is incombustible and in the opposite direction by the products of combustion traveling away from the main patch, the improvement which comprises igniting the first increment of the main patch by forming a pilot patch of combustible mixture in the cylinder prior to the formation of the first increment of the main patch, causing the pilot patch to travel toward the locus of the main patch, and compressing the pilot patch so that it ignites and burns while in said locus and while the first increment of the main patch is present in said locus.

2. Process according to claim 1 wherein the pilot patch is caused to swirl in the cylinder as it is being compressed to bring about its ignition.

3. In operating a reciprocating internal combustion engine wherein fuel is injected into a mass of compressed oxidizing gas that is swirling rapidly relative to the locus of fuel injection to form a localized main patch of combustible mixture in a combustion chamber, the main patch is ignited substantially as soon as it is formed at a location near that of the fuel injection to establish a flame front that tends to travel counter to the direction of swirl with the resulting combustion products traveling in the direction of swirl away from the flame front as additional compressed oxidizing gas swirls toward the main patch and its flame front, and injection of the fuel into the main patch is continued substantially as rapidly as the fuel is consumed therein so that the additional fuel is burned in the main patch while it is confined in one direction by the products of combustion traveling toward the flame front and in the opposite direction by the oxidizing gas which does not yet contain sulficient fuel to be ignitable, the improvement which comprises igniting the main patch by injecting into the swirling mass of oxidizing gas as it is being compressed and before the main patch is formed a pilot jet of fuel to form a pilot patch of combustible mixture which swirls toward the locus of the main patch and is compressed so that it ignites and forms a flame existing in the locality of the main patch at the instant that the first increment of the combustible mixture of the main patch is formed.

4. In operating a reciprocating internal combustion engine involving injecting fuel into a mass of compressed oxidizing gas that is swirling rapidly relative to the locus of fuel injection to form a localized main patch of combustible mixture in a combustion chamber, igniting the main patch substantially as soon as it is formed at a point near the locus of fuel injection to establish a flame front that travels counter to the direction of swirl, the resulting combustion products traveling in the direction of swirl away from the flame front as additional compressed oxidizing gas travels in the direction of swirl toward the main patch and its flame front, and continuing the injection of the fuel into the main patch substantially as rapidly as the fuel is consumed therein so that the additional fuel is burned in the patch which is confined in one direction by the products of combustion travelling away from the flame front and in the opposits direction by the oxidizing gas swirling toward the flame front but into which fuel is not yet injected in sufficient proportion to produce an ignitable mixture, the improvement which comprises injecting a pilot jet of fuel into the swirling oxidizing gas before any of the fuel for the main patch has been injected to form a localized pilot patch of combustible mixture, and compressing this pilot patch so that it ignites and is burning as it swirls and reaches the locus of the main patch and thus ignites the main patch and establishes the flame front.

5. In operating a reciprocating internal combustion engine involving injecting fuel into a mass of compressed oxidizing gas that is swirling rapidly relative to the locus of fuel injection to form a localized main patch of combustible mixture in a combustion chamber, igniting the main patch substantially as soon as it is formed at a point near the locus of fuel injection to establish a flame front that travels counter to the direction of swirl, the resulting combustion products traveling in the direction of swirl away from the flame front as additional compressed oxidizing gas travels in the direction of swirl toward the main patch and its flame front, and continuing the injection of the fuel into the main patch substantially as rapidly as the fuel is consumed therein so that the additional fuel is burned in the main patch while it is confined in one direction by the products of combustion traveling away from the flame front and in the opposite direction by the oxidizing gas traveling toward the flame front but not yet containing sufiicient fuel to be ignitable, the improvement which comprises injecting a pilot jet of fuel into the oxidizing gas to form a localized pilot patch of combustible mixture traveling toward the locus of the main patch before the main patch is formed, and compressing the pilot patch, the degree of compression and the time during which the pilot patch is compressed being such that the pilot patch is burning as it reaches the locus of the main patch and so ignites the main patch and establishes the flame front.

6. Process according to claim in which the fuel injected to form the pilot patch is the same as the fuel injected to form the main patch.

7. Process according to claim 5 in which the fuel injected to form the main patch has a cetane rating that is higher than that of the fuel injected to form the main patch, so that the pilot patch is more readily ignited by compression.

8. In operating a reciprocating internal combustion engine wherein combustion of a combustible mixture in the engine cylinder is localized at each cycle of the engine in a main patch into which fuel is injected substantially as fast as it burned at a flame front of the main patch and which is confined in one direction by oxidizing gas swirling toward the patch and containing so little fuel that it is incombustible and in the opposite direction by the products of combustion swirling away from the flame front of the main patch, the improvement which comprises employing a moving compression-ignited pilot patch of combustible mixture to ignite the main patch during each cycle of the engine until a glow plug disposed at the locus of the main patch has become sufficiently heated by the combustion occurring in the locus during the successive cycles to itself ignite the combustible mixture of successive main patches.

9. In conducting a cycle of a reciprocatin internal combustion engine wherein combustion of a combustible mixture in the cylinder of each engine is localized in each cycle in a main patch into which fuel is injected substantially as fast as it is burned, the main patch being confined in one direction by oxidizing gas swirling toward the patch and containing insufficient fuel to be combustible and in the opposite direction by gaseous products of combustion swirling away from the patch, the improvement which comprises forming a pilot patch of combustible mixture in the cylinder during a cycle before the main 10 patch is formed, compressing the pilot patch to ignite it and causing the ignited pilot patch to ignite the main patch.

10. Process according to claim 9 in which the gas in the cylinder is caused to swirl in each cycle during the compression and power stroke with approximately constant angular velocity so that the pilot patch remains relatively concentrated while it is being compressed to the ignition point.

11. In an internal combustion engine having a cylinder with cylinder head, a piston reciprocable therein and providing a combustion space, means for introducing air into said cylinder and for causing said air to swirl about said combustion space, and means for injecting fuel into one side of the swirling air at a rate coordinated with the air swirl rate to impregnate said swirlin air and immediately form a localized main patch of combustible fuel vapor-air mixture, the combination which comprises means for injecting a pilot jet of fuel into one side of said swirling air during each cycle prior to the injection of fuel to form said main patch of combustible mixture, and means for timing and locating the injection of said pilot jet so that the resulting localized pilot patch of combustible fuel vaporair mixture swirls at least a major portion of the distance around the cylindrical combustion space and is ignited by compression at the time it arrives at the locus of the main patch at the beginning of injection of fuel to form the latter to thereby ignite the first increment of said main patch to establish a flame front, whereby said combustible fuel vapor-air mixture of the main patch is burned at the flame front substantially as rapidly as formed during the continuance of the main patch fuel injection.

12. Apparatus according to claim 11, wherein the air swirl means provides a swirl rate of about six rotations per engine revolution.

13. Apparatus according to claim 11 provided with a glow plug disposed in the cylinder at the locus of the main patch and adapted to be heated by the combustion in the cylinder to a temperature at which it will aid in the ignition of the main patch.

14. Apparatus according to claim 11 provided with a glow plug disposed in the cylinder at the locus of the main patch and adapted to be heated by the combustion in the cylinder to a temperature at which it will bring about the ignition of the main patch, and means for cutting off the pilot jet after such temperature has been attained.

15. Apparatus according to claim 11 in which the fuel for the main patch and the pilot jet are injected at substantially the same location, so that said pilot patch makes substantially one complete swirl around the combustion space before injection of fuel for forming said main patch and ignition of the first increment thereof occurs.

References Cited in the file of this patent UNITED STATES PATENTS Number Country Date 1,239,523 Rogers Sept. 11, 1917 1,392,556 Gottard Oct. 4, 1921 1,767,701 Riehm June 24, 1930 1,820,858 Huber Aug. 25, 1931 2,484,009 Barber Oct. 11, 1949 

